1. Field of the Invention
The present invention relates to an apparatus for processing a progressive scanning video signal, and in particular, to an apparatus for processing a progressive scanning video signal, comprising at least one of a progressive to interlaced signal converter and an interlaced to progressive signal converter, wherein the apparatus therefor is used for television broadcasting systems of the next generation such as the EDTV2 system or the like. In the specification, a progressive scanning video signal is referred to as a progressive scanning signal hereinafter, and an interlaced scanning video signal is referred to as an interlaced scanning signal hereinafter.
2. Description of the Related Art
Recently, as television broadcasting systems of the next generation, progressive scanning signals have been adapted in parts of the EDTV2 system in Japan and the ATV (Advanced Television) proposed system in U.S.A. in addition to a television system having a widened picture screen. Heightening the quality of image in the vertical direction is achieved by using the progressive scanning signals. In the case of the EDTV2 television system having a widened picture screen in Japan, a progressive scanning signal sent from a signal source is converted into an interlaced scanning signal according to a so-called letter box system, and then the converted interlaced scanning signal is transmitted. In this case, the vertical high frequency components of the luminance signal and the high frequency components of the vertical moving picture are superimposed on non-picture portions positioned at the top and bottom of the picture screen (referred to as top and bottom non-picture potions hereinafter), and the image of the letter box signal is displayed on a display unit having an aspect ratio of 4:3 of a television set of the current system. Then a widened picture having an aspect ratio of 16:9 is obtained by the main signal of the center picture in the display unit (referred to as a center main signal hereinafter). Therefore, the EDTV2 system can be compatible with the current broadcasting television system in Japan.
Further, in an existing widened interlaced type television set, the center main signal is enlarged in the vertical direction, resulting in a widened picture on the display unit. However, the vertical resolutions in both the above-mentioned systems deteriorate as compared with that of the picture of the current broadcasting television system.
On the other hand, in a television set for displaying only a widened picture of a progressive scanning signal, a progressive scanning signal is recovered from a main signal and a signal of the top and bottom non-picture portions of the letter box signal which is an interlaced scanning signal, and then a progressive scanning wide picture can be displayed on a display unit thereof. In this case, a picture having a vertical resolution higher than that of the current broadcasting television system can be obtained.
Furthermore, recently, in order to increase the quality of image in addition to widening the picture, video software is recorded, edited or stored in a form of component signals. Thus using the component signals in locations of broadcasting stations is being developed. In this case, in a location of a broadcasting station such as a main adjusting room from which a video signal is transmitted to a television transmission station, the video signal is used in a form of the progressive scanning component signals, and then the progressive scanning component signal is converted into an interlaced scanning letter box signal, which is then transmitted to the television transmission station.
However, almost all the units or apparatuses in the broadcasting stations such as currently used cameras, VTRs, switching units, transmission units and the like are for interlaced scanning signals, and therefore, these units can not process any progressive scanning signal. In order to solve the above-mentioned problems, the following conventional proposed system for processing a progressive scanning signal is disclosed in Akihiko HORI et al., "Component studio system for EDTV", ITE Technical Report, Vol. 17, No. 7, pp. 7-12, BCS'93-2, BFO, in January 1993.
In the conventional proposed system, a progressive scanning signal composed of a luminance signal and two color difference signals is converted into an interlaced scanning signal, so that the luminance signal is divided into a main signal and a sub-signal every one horizontal scanning line so as to be expanded in a time domain of the interlaced scanning system and to be simultaneously outputted in synchronous with each other, so that the two progressive scanning color difference signals are converted into two interlaced scanning signals, respectively, through progressive to interlaced signal conversion. After the progressive scanning signal is thus converted into the interlaced scanning component signals as mentioned above, respective processes are performed on the interlaced scanning component signals within the broadcasting station, and thereafter, the processed interlaced scanning component signals are converted into the progressive scanning signal prior to conversion to the letter box signal.
That is, in the conventional proposed system, the progressive scanning luminance signal is divided into the main signal and the sub-signal every one horizontal scanning line so as to be expanded in a time domain of the progressive scanning system and to be simultaneously outputted in synchronous with each other. This converting method will be described below in detail with reference to FIGS. 10A to 10F,
wherein FIG. 10A shows respective scanning lines of an input progressive scanning signal in blanking intervals and effective intervals;
FIG. 10B shows respective scanning lines of a main signal after progressive to interlaced signal conversion in blanking intervals and effective intervals;
FIG. 10C shows respective scanning lines of a sub-signal after progressive to interlaced signal conversion in blanking intervals and effective intervals;
FIG. 10D shows respective scanning lines of a main signal after interlaced to progressive signal conversion in blanking intervals and effective intervals;
FIG. 10E shows respective scanning lines of a sub-signal after interlaced to progressive signal conversion in blanking intervals and effective intervals; and
FIG. 10F shows respective scanning lines of a combined progressive scanning signal in blanking intervals and effective intervals.
In FIGS. 10A to 10F, respective numbers denote numbers of horizontal scanning lines of the input progressive scanning signal. The incline of respective horizontal scanning lines corresponds to a time interval of horizontal scanning.
In the progressive to interlaced signal conversion shown in FIGS. 10A to 10F, when the horizontal scanning lines of the progressive scanning signal are numbered in an order of 1, 2, 3, . . . from the top line of the blanking interval as shown in FIG. 10A, the top line of the blanking interval of the main signal is numbered as one, whereas the top line of the blanking interval of the sub-signal is numbered as two. Therefore, in the case of the interlaced scanning signal, since an equalizing pulse for a synchronizing signal is added to the top line of the blanking interval, the 525-th line of the first field of the main signal is also over the blanking interval as shown in 900 of FIG. 10B. Accordingly, even though the main signal is combined to the sub-signal and then is converted into the progressive scanning signal as shown in FIGS. 10D and 10E, the resulting progressive scanning signal loses half the information of the 525-th horizontal scanning line as shown in 902 of FIG. 10F. In other words, there is such a problem that the signal of the 525-th horizontal scanning line of the main signal which has been converted into the interlaced scanning signal can not be used upon processing the interlaced scanning signal.
As mentioned above, the information of the 525-th horizontal scanning line which can be utilized as video signal information is lost depending on the converting method in the case of NTSC system.